This proposal focuses on the mechanisms involved in the processing of tonal sequences. One set of experiments would study the organization of the system retaining sequences of tones where such sequences are encoded in terms of acquired pitch alphabets, or scales. Recent work has shown that when such sequences are hierarchically organized the listener is able to infer this organization and so encode them parsimoniously. A model for the encoding and retention of such sequences has been advanced, and several proposed experiments would test predictions from this model. Several further experiments would explore the effects of temporal segmentation and accent on processing such sequences. A second set of proposed experiments is concerned with the abstraction of successive and simultaneous intervals, focusing on the role of octave generalization in such abstractions. These experiments would also examine ease of processing of intervals as a function of their size. A third set of experiments would explore the perceptual consequences of presenting two simultaneous sequences of tones, one to each ear. These experiments would focus on the conditions giving rise to an auditory illusion discovered previously, known as the octave illusion.